The purpose of prayer is not to inform our Lord what you desire, for He knows all your needs. It is to render you able and ready to receive the grace which our Lord will freely give you. This grace cannot be experienced until you have been refined and purified by the fire of desire in devout prayer. For although prayer is not the cause for which our Lord gives grace, it is nevertheless the means by which grace, freely given, comes to the soul.

Book I, ch. 24 (p. 28) - The Ladder of Perfection (1494)